Under considerable daily stresses of life in these days, those individuals who wish to live with a pet are increasing in number, and the number of pet dogs and cats is increasing year after year. On the other hand, with the advancement in veterinary medicine and popularization of pet foods, the number of dogs and cats of advanced age is increasing and, like in humans, the incidence of adult diseases, obesity and nephropathy (renal diseases), among others, is increasing, raising a serious problem. As regards nephropathy, in particular, it is very difficult to recognize a disease signal at an early stage, as suggested by the saying that the kidney is a silent organ. Therefore, upon veterinary examination in view of some or other symptoms, the renal function is found to be in severe disorder in many instances.
In clinical veterinary medicine, the cases of renal diseases have been increasing in recent years with the aging of animals of the family Felidae and, at present, nephropathy is the primary cause of death among family cats. Further, the symptoms of nephropathy are noticed in most cases only when they are already in advanced stages and, thus, the disease is often already in an incurable stage at the time of consultation with a veterinarian. Thus, chronic renal failure is ranked high in the list of causes of deaths of cats.
The clinical symptoms of nephropathy, in particular chronic renal failure, are such general or constitutional symptoms as polyposia and polyuria, anorexia, weight loss, vomiting, diarrhea, dehydration, anemia, and depression. Diagnosis is carried out by or according to an interview with the owner, urinalysis, blood examination, renal biopsy, and imaging, among others. As general indicators of nephropathy, there may be mentioned blood urea nitrogen (hereinafter, BUN), serum creatinin (hereinafter, CRE), and proteinuria. However, accelerative increases in both BUN and CRE are observed only after a decrease in glomerular filtration value (an index in renal function evaluation) to 25% of the normal level or below, hence they cannot serve as markers for early diagnosis. In addition, the BUN is influenced by meals, and the CRE by physical activity. As for the urinary protein, or proteinuria, it is one of findings suggesting disorders of kidneys and is so important that when it is found, nephropathy is suspected first of all. However, while the protein excretion in normal human urine is 3 mg or less/kg/day, the protein excretion in feline urine is as high in concentration as 17.43±9.03 mg/kg/day even in normal conditions. Thus, the equation proteinuria=nephropathy can hardly be formulated.
Under such circumstances, the advent of a marker for early diagnosis of feline nephropathy is now earnestly desired.
The conventional methods of diagnosing nephropathy mainly utilize such complicated techniques as blood examination, radiography of kidneys using a contrast medium, ultrasonic image analysis, and so forth. It is demanded that a more easy and simple method be developed. Further, it is desired that a method by which the owner can check the health status of a cat in a simple and easy manner without visiting a veterinarian and a test kit therefor be developed. A convenient test reagent is also required with which feline nephropathy can easily be found before the disease becomes incurable, with the result that the life of a family cat can be prolonged.